Storage Units: Hard Drives, Floppy Disks, and BIOS Setup
Storage Units: Hard Drives and Floppy Disks
General storage units can permanently store data or programs without needing power. Examples include hard disks and DVDs.
Physical and Logical Structure
The physical structure refers to how the storage medium is divided and where information is stored. It is created during manufacturing. The logical structure is how the information is saved and organized, divided into several zones.
Floppy Disks
A floppy disk is a flexible or floppy magnetic storage medium that permanently stores information. The drive contains an electric motor that moves the disk and read/write heads. Floppy drives are connected to the motherboard with a 34-wire cable.
Physical Structure of a Floppy Disk
Data is stored on a floppy disk in concentric circles called tracks, which are further divided into sectors.
Logical Structure of a Floppy Disk
A cluster is a small group of contiguous sectors on the disk. The cluster size depends on the drive’s size.
Boot Sector
The boot sector is always located in the first sector. It contains a small program that runs when you turn on your computer, allowing it to load. The boot sector also stores a table with information about the disk, such as the number of heads, tracks, sectors per track, and sector size. This table is known as the BIOS Parameter Block.
Configuring in the BIOS Setup
The BIOS setup has an auto-detection option that automatically determines the characteristics of the installed unit. If it fails, it could be due to an incorrectly connected data cable, a disk capacity larger than that permitted by the BIOS, or a damaged disk. IDE hard drives have limitations, requiring changes to the BIOS to overcome them, such as using EBIOS or LBA.
Hard Drives
The two most common types of hard drives are IDE and SATA.
Physical Constitution
Hard drives are the main storage units of a computer, constituting massive storage units. They contain two or more disks stacked on a central axis and isolated from the outside. At the bottom of the hard disk is a printed circuit board that receives commands from the controller. It also ensures that the axis of the disks maintains a steady speed and controls the read/write heads.
The motor typically rotates at 4500 to 7200 RPM. Modern hard drives usually have 2 or 3 magnetic plates. A group of read/write heads is positioned on the surfaces of the plates, aligning with the tracks formed by concentric circles. The heads write information from the disk controller onto the plates by aligning the magnetic particles on their surface. They also read information by detecting the polarity of the aligned particles. When the software and operating system need to read or write to a sector, they send commands to the disk controller to move the read/write heads to the track containing that sector.
Installing Hard Drives
- Configure the hard disk as master or slave on IDE.
- Place the disks in the center of the unit.
- Connect a flat data cable to the IDE (40 to 80 wires) or SATA (7 wires) connector.
- Connect the power supply.
- Set up the partition on the hard disk.
- Format each partition.
- Format the operating system if it’s the main unit.
Physical Structure
A hard disk consists of a series of disks or plates stacked on top of each other in an airtight, dust-free enclosure. The diameter of the plates is between 2 and 3.5 inches. Each plate has two faces, and each face corresponds to a read/write head supported by an arm. There are usually two read/write heads between two disks, and sometimes three on one side.